Jonah Keith

Idaho Fish and Game biologists are applying techniques to restore salmon and steelhead habitat that can reduce the effects of large flood events while also improving agricultural lands.

The way this is done seems counterintuitive — by allowing rivers to flood into areas where they will not cause damage.

During spring floods and large rain events, rivers naturally spill over their banks, creating floodplains and wetlands that provide refuge and food for juvenile salmon and steelhead. As the water moves away from the river and slows down, fine nutrient laden sediment is deposited, enhancing vegetation in the floodplain. This irrigates and fertilizes agricultural lands.

Floodplains which flood regularly can absorb immense amounts of water and have a proven history of lessening large flood events. During historical floods, it is not uncommon to see flows halved downstream of active floodplains. Water absorbed by these lands recharges aquifers and can provide springs that enhance stream flows into the dry season.

Biologists with the Idaho Department of Fish and Game are actively working on restoring floodplains in order to improve juvenile salmon and steelhead survival. In some rivers in Idaho, a lack of juvenile rearing habitat is a major factor limiting their recovery. Activating floodplains would supply necessary refuge for juvenile salmon and steelhead, which require slow-moving habitats to shelter and grow in.

Although these projects are a clear win-win scenario, they have been difficult to implement due to outdated ideas about flood control. This is an important time to share information about this topic so that we can help recover wild salmon and steelhead populations in ways that protect communities from future floods.

Jonah Keith is a Pacific States Marine Fisheries Commission fisheries technician working in cooperation with Idaho Department of Fish and Game to monitor and evaluate ongoing habitat restoration efforts

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